<!DOCTYPE html>
<html lang="zh">
<head>
    <meta charset="UTF-8">
    <title>01-line-height</title>
    <style>
        div {
            /* 文字内容高度就是font-size的大小 */
            font-size: 20px;
            line-height: 2em; /* 2 * 20px = 40px */
            /*line-height: 200%; !* 200% * 20px = 40px*!*/
            /*line-height: 2.5; !* 2.5 * 20px = 50px *!*/
            background-color: #ff0;
            width: 10em; /* 10 * 20px = 200px */
            height: 200px;
        }
    </style>
</head>
<body>

<div>
    我是div <br>
    我是div <br>
    我是div <br>
</div>

</body>
</html>